The successful, wide-spread implementation of optical fibers in telecommunications applications requires the ability to splice two optical fibers end-to-end with a minimum of signal loss. A prerequisite for such splicing is the precise end-to-end alignment of the light transmitting fiber cores. Furthermore, this alignment of the fiber cores must be maintained during the splicing operation.
In the prior art, manual alignment of two optical fibers has been achieved using complex mechanical manipulators to move a first fiber relative to a second fiber while observing the core light transmitted from the first fiber to the second using a photodetector at the far end of the second fiber.
More recently, as disclosed in a publication entitled "Fully Automatic System for the Coupling Alignment of Optical Fibers", by R. Althammer, Optical and Quantum Electronics, Vol. 9, 1977, pages 393-397, the core light transmitted from a first to a second fiber is monitored at the far end of the second fiber and fed back to electronic circuitry. The electronic circuitry selectively actuates stepping monitors to move the abutting fiber ends into optimum alignment. While this approach provides satisfactory results for multimode fibers, the apparatus is not useable for monomode fibers which have smaller core diameters. (See page 394). In addition, the alignment apparatus is unwieldy for field use as access to the far end of the second fiber is not always readily available.
Monomode fibers transmit higher-bit-rate optical signals with less dispersion per unit distance than multimode fibers and provide a significant benefit in high-speed, long-haul transmission systems. Accordingly, apparatus capable of automatically aligning monomode as well as multimode fibers and maintaining the alignment during splicing is very desirable.